1. Field of the Invention
The present invention relates to an engine oil pump, and more particularly, to an engine oil pump that does not make a rapid change in pressure, which may cause surging noise when oil is discharged, by inducing energy consumption of high-pressure oil.
2. Description of Related Art
In general, engine oil pumps supply oil to an engine.
FIG. 4A shows an inner rotor 100 and an outer rotor 200 that are disposed and rotated in a pump case 400, and as shown in the figure, inner rotor 100 and outer rotor 200 form an oil pocket 300, which is a space where oil is filled, when rotating.
Therefore, the pumped oil is discharged out of a discharge portion through oil pocket 300 and supplied to the parts of the engine.
FIG. 4B shows a cross-sectional structure of oil pocket 300, and as shown in the figure, oil pocket 300 is formed on the path through which the oil flows into an oil intake portion 600 and then is discharged to an oil discharge portion 700, separates oil intake portion 600 and oil discharge portion 700, and forms a sealing-forming surface 500 where rotors 100 and 200 come in close contact.
Therefore, the size of oil pocket 300 gradually increases toward sealing-forming surface 500 from oil intake portion 600 in the rotation direction of rotors 100 and 200, and becomes the maximum at sealing-forming surface 500.
Thereafter, oil pocket 300 gradually decreases in size through sealing-forming surface 500 and discharges the oil to the discharge portion.
However, in oil pocket 300, the cross-section is suddenly reduced by sealing-forming surface 500 formed between oil intake portion 600 and oil discharge portion 700, such that when the oil flows from oil intake portion 600 to oil discharge portion 700, pressure is rapidly increased at sealing-forming surface 500, and accordingly, the pressure of the oil in oil pocket 300 is increased.
On the contrary, when the oil flows from sealing-forming surface 500 to oil discharge portion 700, the cross-section suddenly increases at oil discharge portion 700, such that the pressure of the oil is decreased.
As described above, when the change in pressure is large while the oil flows from oil intake portion 600 to oil discharge portion 700 through sealing-forming surface 500, surging noise due to the change in pressure is necessarily generated.
FIG. 4B shows the cross-sectional structure for reducing a change in pressure that causes surging noise, and as shown in the figure, a rapid change in pressure of the oil is prevented by forming a discharge incline at the interface continuing from sealing-forming surface 500 to oil discharge portion 700, such that the magnitude of surging noise is largely reduced.
However, when the discharge incline is used, as described above, the object for preventing a rapid change in pressure can be effectively achieved only when the length of the inclined surface of the discharge incline is sufficiently large, and in order for the effect, it is troublesome to make the length of the inclined surface of the discharge incline different in accordance with the specification of the oil pump, and particularly, an optimum design is necessarily made when the performance of the oil pump is changed, such that continuous optimization is necessary.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.